Eurypterid
Encyclopedia
Eurypterids are an extinct group of arthropod
s related to arachnid
s which include the largest known arthropods that ever lived. They are members of the extinct order Eurypterida (Chelicerata
); which is the most diverse Paleozoic chelicerate order in terms of species. The name Eurypterida comes from the Greek word meaning "broad" or "wide" and the Greek word meaning "wing", for the pair of wide swimming appendages on the first fossil eurypterids discovered. Eurypterids predate the earliest fishes
. The largest, such as Jaekelopterus, reached 2.5 metre or more in length, but most species were less than 20 centimetre. They were formidable predators that thrived in warm shallow water, in both seas and lakes, in the Ordovician
to Permian
from . Although informally called 'sea scorpions', only the earliest ones were marine (later ones lived in brackish or freshwater), and they were not true scorpion
s. According to theory, the move from the sea to fresh water probably occurred by the Pennsylvanian
subperiod. Eurypterids are believed to have undergone ecdysis
, making their significance in ecosystems difficult to assess, because it can be difficult to tell a fossil moult from a true fossil carcass. They went extinct during the Permian–Triassic extinction event , and their fossils have a near global distribution.
About two dozen families of eurypterids are known. Perhaps the best-known genus of eurypterid is Eurypterus
, of which around 16 fossil species are known. The genus Eurypterus was created in 1825 by James Ellsworth De Kay
, a zoologist. He recognized the arthropod nature of the first ever described eurypterid specimen, found by Dr. S. L. Mitchill. In 1984, that species, Eurypterus remipes was named the state fossil of New York.
The typical eurypterid had a large, flat, semicircular carapace
, followed by a jointed section, and finally a tapering, flexible tail, most ending with a long spine at the end (Pterygotus
, though, had a large flat tail, possibly with a smaller spine). Behind the head of the eurypterids were twelve body segments. These segments are formed by a dorsal plate called tergite, and a ventral plate called sternite. The tail, known as the telson
, is spiked in most eurypterids like in modern scorpion
s and in some species it may have been used to inject venom
, but so far there is no certain evidence any eurypterids were venomous. Most eurypterids have paddles toward the end of the carapace and beyond, which were used to propel themselves through water. The suborder Stylonurina have walking legs instead of paddles. Some argue that the paddles were also used for digging. It is possible that it was used for both. Underneath, in addition to the pair of swimming appendages the creature had 4 pairs of jointed legs
for walking, and two claws at the front, chelicerae
, which were enlarged in pterygotids. The walking legs had odd hairs, similar to modern day crabs. Other features, common to ancient and modern arthropods of this type, include one pair of compound eyes and a pair of smaller eyes called ocelli, between the other larger pair of eyes.
Many eurypterids had legs large and long enough to do more than allow them to crawl over the sea bottom; a number of species (particularly hibbertopterids) had large stout legs, and were probably capable of terrestrial locomotion (like land crab
s today). Studies of what are believed to be their trackways
indicate that eurypterids used in-phase, hexapodous (six-legged) and octopodous (eight-legged) gaits. Some species may have been amphibious, emerging onto land for at least part of their life cycle; they may have been capable of breathing both in water and in air. A predatory arthropod
whose traces are known as Protichnites
, found in Cambrian strata dating from , is a possible stem group eurypterid, and is among the first evidence of animals on land.
Among the largest eurypterids are the hibbertopteroids, named after the British palaeontologist Dr. Samuel Hibbert, who described Hibbertopterus
scouleri at the East Kirkton limestone quarry
in Scotland in 1836. Fossil tracks (a form of trace fossil
) were identified recently in East Lothian
, Scotland, as made by a 1.6 metre long Hibbertopterus
. The largest well-described genus of sea-scorpion was Pterygotus
, an arthropod the size of a crocodile. Fossils of Pterygotus
are relatively common although complete fossils are rare. At 2.1 metres (6.9 ft) long, they were until recently the largest known arthropod ever to have lived. Their fossils have been found worldwide, except in Antarctica. In 2007, a 46 cm (18.1 in) claw belonging to Jaekelopterus rhenaniae
(a species originally described in 1914) was discovered by a group of paleontologists led by Simon Braddy at the University of Bristol
, indicating that J. rhenaniae was 2.5 m (8.2 ft) in length, making it the largest arthropod ever found.
s, together forming a group called Merostomata
. Subsequent studies placed eurypterids closer to the arachnid
s in a group called Metastomata. There has also been a prevailing idea that eurypterids are closely related to scorpion
s, which they resemble. This hypothesis is reflected in the common name 'sea scorpion'. More recently it has been recognised that a little-known, extinct group called Chasmataspida
also shares features with Eurypterida, and the two groups were sometimes confused with one another. The most recent summary of relationships between arachnids and their relatives recognised Eurypterida, Xiphosura and Arachnida as three major groups, but was not able to resolve details between them.
There are 246 valid species of eurypterids as of 2011. All of them are extinct. They are grouped into the following:
Suborder Stylonurina Diener, 1924
Suborder Eurypterina Burmeister, 1843
The trace fossil
trackways produced by eurypterids are placed in the ichnogenus Palmichnium.
presented here is simplified from a study by Tetlie. The most important phylogenetic breakdown is based on the two major innovations that characterise the evolution of the eurypterids. The most important was the transformation of the posteriormost prosomal appendage into a swimming paddle (as found in the clade Eurypterina). The second innovation was the enlargement of the chelicerae
, (as found in the family Pterygotidae), allowing these appendages to be used for active prey capture.
75% of eurypterid species are eurypterines; this represents 99% of specimens. The superfamily Pterygotioidea is the most species-rich clade with 56 species, followed by the Adelophthalmoidea with 43 species; as sister taxa, they comprise the most derived eurypterids. Pterygotioidea includes the pterygotids, which are the only eurypterids to have a cosmopolitan distribution. This clade is one of the best supported within the eurypterids.
It has been suggested that the development of dermal armour in certain groups of jawless vertebrates (such as the Heterostraci
and the Osteostraci
) is in response to predation
pressure by increasingly sophisticated eurypterid predators (specifically the pterygotids) although this has yet to be verified by detailed analysis. An increase in fish
diversity is tied to a decline in eurypterid diversity in the Lower Devonian, although it is not thought that this represents competitive replacement; in fact, this is rare in the fossil record.
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s related to arachnid
Arachnid
Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...
s which include the largest known arthropods that ever lived. They are members of the extinct order Eurypterida (Chelicerata
Chelicerata
The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda, and includes horseshoe crabs, scorpions, spiders and mites...
); which is the most diverse Paleozoic chelicerate order in terms of species. The name Eurypterida comes from the Greek word meaning "broad" or "wide" and the Greek word meaning "wing", for the pair of wide swimming appendages on the first fossil eurypterids discovered. Eurypterids predate the earliest fishes
Prehistoric fish
Prehistoric fish refers to early fish that are known only from fossil records. They are the earliest known vertebrates, and include the first and extinct fish that lived through the Cambrian to the Tertiary. The study of prehistoric fish is called paleoichthyology...
. The largest, such as Jaekelopterus, reached 2.5 metre or more in length, but most species were less than 20 centimetre. They were formidable predators that thrived in warm shallow water, in both seas and lakes, in the Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
to Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
from . Although informally called 'sea scorpions', only the earliest ones were marine (later ones lived in brackish or freshwater), and they were not true scorpion
Scorpion
Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...
s. According to theory, the move from the sea to fresh water probably occurred by the Pennsylvanian
Pennsylvanian
The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...
subperiod. Eurypterids are believed to have undergone ecdysis
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
, making their significance in ecosystems difficult to assess, because it can be difficult to tell a fossil moult from a true fossil carcass. They went extinct during the Permian–Triassic extinction event , and their fossils have a near global distribution.
About two dozen families of eurypterids are known. Perhaps the best-known genus of eurypterid is Eurypterus
Eurypterus
Eurypterus is an extinct genus of sea scorpions. They existed during the Silurian Period, from around 432 to 418 million years ago.There are fifteen species belonging to the genus Eurypterus, the most common of which is Eurypterus remipes, the first eurypterid fossil discovered and the state...
, of which around 16 fossil species are known. The genus Eurypterus was created in 1825 by James Ellsworth De Kay
James Ellsworth De Kay
James Ellsworth De Kay was an American zoologist.-Biography:...
, a zoologist. He recognized the arthropod nature of the first ever described eurypterid specimen, found by Dr. S. L. Mitchill. In 1984, that species, Eurypterus remipes was named the state fossil of New York.
Body structure
Eurypterids have been formally described as follows:"Small to very large merostomes with elongate lanceolate, rarely trilobed body; prosoma [head] of moderate size; opisthosoma [body] with 12 moveable segments and styliform to spatulate telson [tail], with division commonly into 7-segmented preabdomen and 5-segmented postabdomen; prosomal [head] appendages 6, comprising 3-jointed chelicerae, walking legs, the last pair commonly transformed into swimming legs. Mouth central, bordered posteriorly by endostoma and metastoma. Operculum with median genital appendage, abdominal appendages plate-shaped with nonlaminate gills. Ordovician-Permian."
The typical eurypterid had a large, flat, semicircular carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
, followed by a jointed section, and finally a tapering, flexible tail, most ending with a long spine at the end (Pterygotus
Pterygotus
Pterygotus is the second-largest known eurypterid, or sea scorpion and one of the largest arthropods of all time.-Description:...
, though, had a large flat tail, possibly with a smaller spine). Behind the head of the eurypterids were twelve body segments. These segments are formed by a dorsal plate called tergite, and a ventral plate called sternite. The tail, known as the telson
Telson
The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...
, is spiked in most eurypterids like in modern scorpion
Scorpion
Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...
s and in some species it may have been used to inject venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
, but so far there is no certain evidence any eurypterids were venomous. Most eurypterids have paddles toward the end of the carapace and beyond, which were used to propel themselves through water. The suborder Stylonurina have walking legs instead of paddles. Some argue that the paddles were also used for digging. It is possible that it was used for both. Underneath, in addition to the pair of swimming appendages the creature had 4 pairs of jointed legs
Arthropod leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...
for walking, and two claws at the front, chelicerae
Chelicerae
The chelicerae are mouthparts of the Chelicerata, an arthropod subphylum that includes arachnids, Merostomata , and Pycnogonida . Chelicerae are pointed appendages which are used to grasp food, and are found in place of the chewing mandibles most other arthropods have...
, which were enlarged in pterygotids. The walking legs had odd hairs, similar to modern day crabs. Other features, common to ancient and modern arthropods of this type, include one pair of compound eyes and a pair of smaller eyes called ocelli, between the other larger pair of eyes.
Land crab
Gecarcinidae is a family of true crabs that are adapted for terrestrial existence, commonly known as land crabs. Similar to all other crabs, land crabs possess a series of gills. In addition, the part of the carapace covering the gills is inflated and equipped with blood vessels. These organs...
s today). Studies of what are believed to be their trackways
Fossil trackway
A fossil trackway is a type of trace fossil, a trackway made by an organism. Many fossil trackways were made by dinosaurs, early tetrapods, and other quadrupeds and bipeds on land...
indicate that eurypterids used in-phase, hexapodous (six-legged) and octopodous (eight-legged) gaits. Some species may have been amphibious, emerging onto land for at least part of their life cycle; they may have been capable of breathing both in water and in air. A predatory arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
whose traces are known as Protichnites
Protichnites
Protichnites is a genus of trace fossil consisting of the imprints made by the walking activity of arthropods. It is likely that more than one type of arthropod was responsible for these tracks. Euthycarcinoids, aglaspidids and eurypterids are possible contributors. Protichnites consists of two...
, found in Cambrian strata dating from , is a possible stem group eurypterid, and is among the first evidence of animals on land.
Among the largest eurypterids are the hibbertopteroids, named after the British palaeontologist Dr. Samuel Hibbert, who described Hibbertopterus
Hibbertopterus
Hibbertopterus is a genus of giant sea scorpion that inhabited the swamps of Scotland during the Carboniferous.Hibbertopterus is a member of the family Hibbertopteridae, large bizarre Eurypterids found from the Upper Devonian to the end of the Permian period...
scouleri at the East Kirkton limestone quarry
East Kirkton Quarry
East Kirkton Quarry is a former limestone quarry, now better known as a fossil site known for terrestrial fossils from the fossil-poor "Romer's gap, a 15 million year period at the beginning of the Carboniferous...
in Scotland in 1836. Fossil tracks (a form of trace fossil
Trace fossil
Trace fossils, also called ichnofossils , are geological records of biological activity. Trace fossils may be impressions made on the substrate by an organism: for example, burrows, borings , urolites , footprints and feeding marks, and root cavities...
) were identified recently in East Lothian
East Lothian
East Lothian is one of the 32 council areas of Scotland, and a lieutenancy Area. It borders the City of Edinburgh, Scottish Borders and Midlothian. Its administrative centre is Haddington, although its largest town is Musselburgh....
, Scotland, as made by a 1.6 metre long Hibbertopterus
Hibbertopterus
Hibbertopterus is a genus of giant sea scorpion that inhabited the swamps of Scotland during the Carboniferous.Hibbertopterus is a member of the family Hibbertopteridae, large bizarre Eurypterids found from the Upper Devonian to the end of the Permian period...
. The largest well-described genus of sea-scorpion was Pterygotus
Pterygotus
Pterygotus is the second-largest known eurypterid, or sea scorpion and one of the largest arthropods of all time.-Description:...
, an arthropod the size of a crocodile. Fossils of Pterygotus
Pterygotus
Pterygotus is the second-largest known eurypterid, or sea scorpion and one of the largest arthropods of all time.-Description:...
are relatively common although complete fossils are rare. At 2.1 metres (6.9 ft) long, they were until recently the largest known arthropod ever to have lived. Their fossils have been found worldwide, except in Antarctica. In 2007, a 46 cm (18.1 in) claw belonging to Jaekelopterus rhenaniae
Jaekelopterus rhenaniae
Jaekelopterus rhenaniae is an extinct species of the Eurypterida . At an estimated length of 2.5 meters , it is one of the two largest arthropods ever discovered...
(a species originally described in 1914) was discovered by a group of paleontologists led by Simon Braddy at the University of Bristol
University of Bristol
The University of Bristol is a public research university located in Bristol, United Kingdom. One of the so-called "red brick" universities, it received its Royal Charter in 1909, although its predecessor institution, University College, Bristol, had been in existence since 1876.The University is...
, indicating that J. rhenaniae was 2.5 m (8.2 ft) in length, making it the largest arthropod ever found.
Relationships with other groups
Eurypterids have traditionally been regarded as close relatives of horseshoe crabHorseshoe crab
The Atlantic horseshoe crab, Limulus polyphemus, is a marine chelicerate arthropod. Despite its name, it is more closely related to spiders, ticks, and scorpions than to crabs. Horseshoe crabs are most commonly found in the Gulf of Mexico and along the northern Atlantic coast of North America...
s, together forming a group called Merostomata
Merostomata
Merostomata is the name given to a grouping of the extinct Eurypterida and the Xiphosura . The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended by Henry Woodward to cover both groups....
. Subsequent studies placed eurypterids closer to the arachnid
Arachnid
Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...
s in a group called Metastomata. There has also been a prevailing idea that eurypterids are closely related to scorpion
Scorpion
Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...
s, which they resemble. This hypothesis is reflected in the common name 'sea scorpion'. More recently it has been recognised that a little-known, extinct group called Chasmataspida
Chasmataspida
Chasmataspidida are a rare, extinct group of chelicerate arthropods. They are probably related to either horseshoe crabs and/or sea scorpions...
also shares features with Eurypterida, and the two groups were sometimes confused with one another. The most recent summary of relationships between arachnids and their relatives recognised Eurypterida, Xiphosura and Arachnida as three major groups, but was not able to resolve details between them.
List of families and genera
There are 246 valid species of eurypterids as of 2011. All of them are extinct. They are grouped into the following:
Suborder Stylonurina Diener, 1924
- Superfamily Rhenopteroidea Størmer, 1951
-
-
- RhenopteridaeRhenopteridaeRhenopteridae are an extinct family of prehistoric eurypterids that lived in the Lower Devonian period in Europe and possibly North America.-Description:...
Størmer, 1951
-
- Alkenopterus Størmer, 1974
- Brachyopterella Kjellesvig-Waering, 1966
- BrachyopterusBrachyopterusBrachyopterus is a genus of prehistoric eurypterid of the family Rhenopteridae.-Description:Brachyopterus is distinguished by its small size, compound eyes with axes converging anteriorly on a subtrapezoid to subpentagonal prosoma...
Størmer, 1951 - Kiaeropterus Waterston, 1979
- Leiopterella Lamsdell, Braddy, Loeffler, & Dineley, 2010
- RhenopterusRhenopterusRhenopterus is an extinct prehistoric eurypterid. Rhenopterus lived in the Lower Devonian period in Europe and possibly North America.-Description:...
Størmer, 1936- Superfamily StylonuroideaStylonuroideaStylonuroidea are an extinct superfamily of eurypterids. They were members of the subphylum Chelicerata.-Description:Stylonuroidea, which lived from the Ordovician to Lower Permian periods, were characterized by their last pair of prosomal appendages, which were developed as walking legs, or less...
Kjellesvig-Waering, 1959
- Superfamily Stylonuroidea
- Parastylonuridae Waterston, 1979
-
- Parastylonurus Kjellesvig-Waering, 1966
- Stylonurella Kjellesvig-Waering, 1966
- StylonuridaeStylonuridaeStylonuridae are an extinct family of prehistoric eurypterids within the Superfamily Stylonuroidea.-Description:Stylonuridae, which lived from the Ordovician to Lower Permian periods, were small to very large forms with scales developing into tubercules and knobs. The prosoma exhibited variable...
Diener, 1924
-
- CtenopterusCtenopterusCtenopterus is a genus of prehistoric eurypterid of the Family Stylonuridae. It contains only one species.-Description:Stylonurids, which lived from the Ordovician to Lower Permian periods, were small to very large forms with scales developing into tubercules and knobs. The prosoma exhibited...
Clarke & Ruedemann, 1912 - Laurieipterus Kjellesvig-Waering, 1966
- Pagea Waterston, 1962
- StylonurusStylonurusStylonurus is a genus of prehistoric eurypterid of the Family Stylonuridae.-Description:Stylonurids, which lived from the Ordovician to Lower Permian periods, were small to very large forms with scales developing into tubercules and knobs. The prosoma exhibited variable shape, with arcuate...
Page, 1856- Superfamily Kokomopteroidea Kjellesvig-Waering, 1966
- Ctenopterus
- Kokomopteridae Kjellesvig-Waering, 1966
-
- Kokomopterus Kjellesvig-Waering, 1966
- Lamontopterus Waterston, 1979
- Hardieopteridae Tollerton, 1989
-
- Hallipterus Kjellesvig-Waering, 1963
- TarsopterellaTarsopterellaTarsopterella is a genus of prehistoric eurypterid of the Family Hardieopteridae. It contains only one species.-Description:Tarsopterella is distinguished by its prosoma , which is subrectangular and slightly concave in front, with small compound eyes. Its abdomen has pronounced lateral epimera...
Størmer, 1951- Superfamily Hibbertopteroidea Kjellesvig-Waering, 1959
- Drepanopteridae Kjellesvig-Waering, 1966
-
- DrepanopterusDrepanopterusDrepanopterus is an extinct genus of eurypterid. There are currently two species assigned to the genus. The genus has in the past been assigned its own family, with nine species associated with the genus Drepanopterus, however five of these have since been proven to be synonyms of pre-existing...
Laurie, 1892
- Drepanopterus
- Hibbertopteridae Kjellesvig-Waering, 1959
-
- CampylocephalusCampylocephalusCampylocephalus is a genus of prehistoric eurypterid of the Family Hibbertopteridae.-Description:Campylocephalus is distinguished by its prosoma , which is subsemicircular and strongly convex, with subcentral compound eyes separated by inflated lobes. Its abdominal tergites are convex, with...
Eichwald, 1860 - Cyrtoctenus Størmer & Waterston, 1968
- Dunsopterus Waterston, 1968
- HastimimaHastimimaHastimima is a genus of prehistoric eurypterid of the Family Hibbertopteridae. It contains only one species, Hastimima whitei, recovered from the Permian period of Brazil....
White, 1908 - HibbertopterusHibbertopterusHibbertopterus is a genus of giant sea scorpion that inhabited the swamps of Scotland during the Carboniferous.Hibbertopterus is a member of the family Hibbertopteridae, large bizarre Eurypterids found from the Upper Devonian to the end of the Permian period...
Kjellesvig-Waering, 1959 - Vernonopterus Waterston, 1957
- Campylocephalus
- Mycteroptidae Cope, 1886
-
- MegarachneMegarachneMegarachne servinei, the only species belonging to the genus Megarachne, was an Upper Carboniferous eurypterid found near Córdoba, Argentina. It was originally described as a spider with a body length of , which would have made it the largest spider ever to have existed...
Hünicken, 1980 - MycteropsMycteropsMycterops is a genus of prehistoric eurypterid of the Family Mycteroptidae. Mycterops lived in the Carboniferous period in Europe and North America.-Description:...
Cope, 1886 - Woodwardopterus Kjellesvig-Waering, 1959
- Incertae sedisIncertae sedis, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
- Incertae sedis
- Stylonuroides Kjellesvig-Waering, 1966
- Megarachne
- Rhenopteridae
-
Suborder Eurypterina Burmeister, 1843
- Plesion taxa
-
-
-
- OnychopterellaOnychopterellaOnychopterella is a genus of prehistoric eurypterid in the Family Eurypteridae.- Description :Eurypteridae, which lived from the Ordovician to the Late Carboniferous period, were characterized by small to large exoskeletons with inconspicuous semilunar scales or curved ridges. The telson, was...
Størmer, 1951- Superfamily Moselopteroidea Lamsdell, Braddy, & Tetlie, 2010
- Onychopterella
- Moselopteridae Lamsdell, Braddy, & Tetlie, 2010
-
- Moselopterus Størmer, 1974
- Vinetopterus Poschmann & Tetlie, 2004
- Superfamily Megalograptoidea Caster & Kjellesvig-Waering, 1955
- MegalograptidaeMegalograptidaeMegalograptidae is a family of extinct eurypterids.-Description:Megalograptids were characterized by large exoskeletons with ovate to triangular scales. The prosoma was subquadrate, with a tonguelike anterior process bearing marginal spines, and compound eyes on the top front of the head. The...
Caster & Kjellesvig-Waering, 1955
-
- EchinognathusEchinognathusEchinognathus is a genus of prehistoric eurypterid in the Family Megalograptidae. Echinognathus is known from the Ordovician.-Description:...
Walcott, 1882 - MegalograptusMegalograptusMegalograptus is a Ordovician eurypterid , and was among the earliest known genera . The generic name is derived from the fact that its first fossils were of its very spiny legs, which were mistaken for massive graptolites. It lived from 460 to 445 mya...
Miller, 1874- Superfamily EurypteroideaEurypteroideaEurypteroidea are an extinct superfamily of eurypterids.-Description:Eurypteroidea, which lived from the Ordovician to Permian periods, were characterized by their last pair of prosomal appendages, which were developed as swimming legs, carrying paddles formed by the expansion of the two...
Burmeister, 1843
- Superfamily Eurypteroidea
- Echinognathus
- DolichopteridaeDolichopteridaeDolichopteridae are an extinct family of eurypterids that lived in the Silurian and Devonian periods.-Description:Dolichopteridae had outer surfaces that were either smooth or with pustules and semilunar scales. Their compound eyes were arcuate and located anteriorly on the prosoma . Their...
Kjellesvig-Waering & Størmer, 1952
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- DolichopterusDolichopterusDolichopterus is a genus of the prehistoric sea scorpions, arthropods in the order Eurypterida.-Distribution:It lived in the Late Silurian in shelf or epicontinental seas of the region where Avalonia, Baltica and Laurentia met during the Caledonian orogeny; its fossils have been found in...
Hall, 1859 - Ruedemannipterus Kjellesvig-Waering, 1966
- Buffalopterus Kjellesvig-Waering & Heubusch, 1962
- StrobilopterusStrobilopterusStrobilopterus is a genus of prehistoric eurypterid of the family Dolichopteridae.-Description:Dolichopterids, which lived in the Silurian and Devonian periods, were medium-sized, and had outer surfaces that were either smooth with pustules and semilunar scales. Their compound eyes were arcuate...
Ruedemann, 1935 - Syntomopterus Kjellesvig-Waering, 1961
- Dolichopterus
- EurypteridaeEurypteridaeEurypteridae are an extinct family of eurypterids. They were members of the superfamily Eurypteroidea.-Description:Eurypteridae, which lived during the Silurian period, were characterized by small to large exoskeletons with inconspicuous semilunar scales or curved ridges. The telson, was...
Burmeister, 1843
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- EurypterusEurypterusEurypterus is an extinct genus of sea scorpions. They existed during the Silurian Period, from around 432 to 418 million years ago.There are fifteen species belonging to the genus Eurypterus, the most common of which is Eurypterus remipes, the first eurypterid fossil discovered and the state...
De Kay, 1825
- Eurypterus
- Erieopteridae Tollerton, 1989
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- Erieopterus Kjellesvig-Waering, 1958
- Superfamily Mixopteroidea Caster & Kjellesvig-Waering, 1955
- Erieopterus Kjellesvig-Waering, 1958
- CarcinosomatidaeCarcinosomatidaeCarcinosomatidae is a family of extinct arthropods in the class Eurypterida. Up to long, these eurypterids are found from the Ordovician to the Devonian periods.-Description:...
Størmer, 1934
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- CarcinosomaCarcinosomaCarcinosoma is a genus of an extinct arthropod. Up to 30 cm long, these eurypterids were found in New York and in other states of the United States. It is from the Late Silurian.-Description:...
Claypole, 1890 - Eocarcinosoma Caster & Kjellesvig-Waering, 1964
- Paracarcinosoma Caster & Kjellesvig-Waering, 1964
- RhinocarcinosomaRhinocarcinosomaRhinocarcinosoma is a genus of Silurian eurypterid, with a triangular carapace, laterally positioned eyes, and a curved telson. In 2002, a new species was described from the Dô Son Formation of the Dô Son Peninsula of northern Vietnam.-Species:...
Novojilov, 1962
- Carcinosoma
- Micopteridae Caster & Kjellesvig-Waering, 1955
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- Lanarkopterus Ritchie, 1968
- MixopterusMixopterusMixopterus is a genus of a eurypterid. It belongs to the family Mixopteridae.-Description:Mixopterus were characterised by a robust exoskeletons with scattered tubercles or semicircular scales. The prosoma was subquadrate, protruding antemedially. The chelicerae were small...
Ruedemann, 1921- Superfamily Waeringopteroidea
- Waeringopteridae (not formally published)
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- GrossopterusGrossopterusGrossopterus is a genus of prehistoric eurypterid of the Family Waeringopteridae.-Species:Two species are currently classified under the genus:*Grossopterus Størmer, 1934 **Grossopterus overathi — Devonian, Germany...
Størmer, 1934 - Orcanopterus Stott, Tetlie, Braddy, Nowlan, Glasser, & Devereux, 2005
- Waeringopterus Leutze, 1961
- Superfamily Adelophthalmoidea Tollerton, 1989
- Grossopterus
- Adelophthalmidae Tollerton, 1989
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- Adelophthalmus Jordan in Jordan & von Mayer, 1854
- Bassipterus Kjellesvig-Waering & Leutze, 1966
- Eysyslopterus Tetlie & Poschmann, 2008
- Nanahughmilleria Kjellesvig-Waering, 1961
- Parahughmilleria Kjellesvig-Waering, 1961
- Pittsfordipterus Kjellesvig-Waering & Leutze, 1966
- Superfamily Pterygotioidea Clarke & Ruedemann, 1912
- Hughmilleriidae Kjellesvig-Waering, 1951
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- Herefordopterus Tetlie, 2006
- HughmilleriaHughmilleriaHughmilleria is a genus of Silurian eurypterid. The genus name commemorates the Scottish geologist Hugh Miller.-Stratigraphy and ecology:Fossils of Hughmilleria have been found in Silurian deposits from the Llandovery and Ludlow epochs...
Sarle, 1902
- Slimonidae Novojilov, 1968
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- SlimoniaSlimoniaSlimonia is a genus of Silurian eurypterid roughly similar to the genus Pterygotus. Slimonia resembled Pterygotus, save that the former's telson is larger, and that its body was smaller and more slender than the latter. Unlike Pterygotus, which lived in estuaries, Slimonia species lived...
Page, 1856 - SalteropterusSalteropterusSalteropterus is a genus of prehistoric eurypterid of the family Slimonidae. Salteropterus lived in the Silurian period, and specimens have been recovered in Britain.-Description:...
Kjellesvig-Waering, 1951
- Slimonia
- PterygotidaePterygotidaePterygotidae are an extinct family of eurypterids. They were members of the superfamily Pterygotioidea, and were the only eurypterids to have a truly worldwide distribution, and include the largest arthropods to have ever lived.-Description:...
Clarke & Ruedemann, 1912
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- PterygotusPterygotusPterygotus is the second-largest known eurypterid, or sea scorpion and one of the largest arthropods of all time.-Description:...
Agassiz, 1839 - AcutiramusAcutiramusAcutiramus is an extinct genus of eurypterid which lived in the Late Silurian to Early Devonian.Acutiramus was one of the largest eurypterids with pincers 5 cm and length about 2 m...
Ruedemann, 1935 - Ciurcopterus Tetlie & Briggs, 2009
- ErettopterusErettopterusErettopterus is a genus of prehistoric eurypterid. It was related to another large eurypterid, Pterygotus.-Description:Pterygotidae, which lived from the Ordovician to Devonian periods, were characterized by small to large exoskeletons with semilunar scales. The telson, was expanded, or flatter...
Salter in Huxley & Salter, 1859 - Jaekelopterus Waterston, 1964
- Incertae sedisIncertae sedis, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
- Incertae sedis
- Clarkiepterus Kjellesvig-Waering, 1966
- Dorfopterus Kjellesvig-Waering, 1955
- Holmipterus Kjellesvig-Waering, 1979
- Marsupipterus Caster & Kjellesvig-Waering, 1955
- TylopterellaTylopterellaTylopterella is a genus of prehistoric eurypterid which lived from the Ordovician to the Upper Carboniferous period. It is of uncertain taxonomic placement within the order Eurypterida.-Description:...
Størmer, 1951 - Unionopterus Chernyshev, 1948
- Pterygotus
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The trace fossil
Trace fossil
Trace fossils, also called ichnofossils , are geological records of biological activity. Trace fossils may be impressions made on the substrate by an organism: for example, burrows, borings , urolites , footprints and feeding marks, and root cavities...
trackways produced by eurypterids are placed in the ichnogenus Palmichnium.
Phylogeny
The cladogramCladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
presented here is simplified from a study by Tetlie. The most important phylogenetic breakdown is based on the two major innovations that characterise the evolution of the eurypterids. The most important was the transformation of the posteriormost prosomal appendage into a swimming paddle (as found in the clade Eurypterina). The second innovation was the enlargement of the chelicerae
Chelicerae
The chelicerae are mouthparts of the Chelicerata, an arthropod subphylum that includes arachnids, Merostomata , and Pycnogonida . Chelicerae are pointed appendages which are used to grasp food, and are found in place of the chewing mandibles most other arthropods have...
, (as found in the family Pterygotidae), allowing these appendages to be used for active prey capture.
75% of eurypterid species are eurypterines; this represents 99% of specimens. The superfamily Pterygotioidea is the most species-rich clade with 56 species, followed by the Adelophthalmoidea with 43 species; as sister taxa, they comprise the most derived eurypterids. Pterygotioidea includes the pterygotids, which are the only eurypterids to have a cosmopolitan distribution. This clade is one of the best supported within the eurypterids.
It has been suggested that the development of dermal armour in certain groups of jawless vertebrates (such as the Heterostraci
Heterostraci
Heterostraci is an extinct class of jawless vertebrate that lived primarily in marine and estuary environments. They arose during the Ordovician, and all, save for the Psammosteids, became extinct during the late Devonian...
and the Osteostraci
Osteostraci
The class Osteostraci was a group of bony-armored jawless fish, termed "ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian....
) is in response to predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
pressure by increasingly sophisticated eurypterid predators (specifically the pterygotids) although this has yet to be verified by detailed analysis. An increase in fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
diversity is tied to a decline in eurypterid diversity in the Lower Devonian, although it is not thought that this represents competitive replacement; in fact, this is rare in the fossil record.
See also
- List of eurypterids
- NepidaeNepidaeNepidae is a family of insects in the order Hemiptera, suborder Heteroptera. They are commonly called waterscorpions for their superficial resemblance to a scorpion, which is due to the raptorial forelegs and the presence of a long slender process at the posterior end of the abdomen, simulating a...
– an unrelated insect, commonly known as a "water scorpion" - HibbertopterusHibbertopterusHibbertopterus is a genus of giant sea scorpion that inhabited the swamps of Scotland during the Carboniferous.Hibbertopterus is a member of the family Hibbertopteridae, large bizarre Eurypterids found from the Upper Devonian to the end of the Permian period...